title: The influence of beta-arrestin2 on cannabinoid CB1 receptor coupling to G-proteins and subcellular localization and relative levels of beta-arrestin1 and 2 in mouse brain.
abstract: BACKGROUND
  Beta-arrestins are known to couple to some G-protein-coupled receptors (GPCRs) to regulate receptor internalization, G-protein coupling and signal transduction, but have not been investigated for most receptors, and for very few receptors in vivo. Previous studies have shown that beta-arrestin2 deletion enhances the efficacy of specific cannabinoid agonists.
  
  
  OBJECTIVE
  The present study hypothesized that brain cannabinoid CB1 receptors are regulated by beta-arrestin2.
  
  
  METHODS
  Beta-arrestin2+/+ and -/- mice were used. Western blotting was used to determine the relative levels of each beta-arrestin subtype in mouse brain. Receptor binding was measured to determine whether deletion of beta-arrestin2 influences agonist binding to brain CB1 receptors, or the subcellular localization of CB1 in brain membranes subjected to differential centrifugation. A variety of cannabinoid agonists from different chemical classes were investigated for their ability to activate G-proteins in the presence and absence of beta-arrestin2 in cerebellum, hippocampus and cortex.
  
  
  RESULTS
  No differences were found in the density of beta-arrestin1 or cannabinoid CB1 receptors in several brains of beta-arrestin2+/+ versus -/- mice. Differences between genotypes were found in the proportion of high- and low-affinity agonist binding sites in brain areas that naturally express higher levels of beta-arrestin2. Cortex from beta-arrestin2-/- mice contained less CB1 in the P1 fraction and more CB1 in the P2 fraction compared to beta-arrestin2+/+. Of the agonists assayed for activity, only Δ(9)-tetrahydrocannabinol (THC) exhibited a difference between genotypes, in that it was less efficacious in beta-arrestin2-/- than +/+ mouse membranes.
  
  
  CONCLUSIONS
  Beta-arrestin2 regulates cannabinoid CB1 receptors in brain.
authors.affiliation: Department of Pharmaceutical Sciences, Campbell University College of Pharmacy & Health Sciences , NC , USA .
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Breivogel
authors.forename: Vanita
authors.initials: V
authors.lastname: Puri
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Lambert
authors.forename: Deryck K
authors.initials: DK
authors.lastname: Hill
authors.forename: John W
authors.initials: JW
authors.lastname: Huffman
authors.forename: Raj K
authors.initials: RK
authors.lastname: Razdan
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism*; D001921:Brain / Q000378:metabolism / Q000473:pathology; D063386:Cannabinoid Receptor Agonists / Q000378:metabolism; D002460:Cell Line; D051379:Mice; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D063386:Cannabinoid Receptor Agonists; D043884:Receptor, Cannabinoid, CB1; D043562:Receptors, G-Protein-Coupled; D000071557:beta-Arrestins